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Nature 415, 963 (2002)
The future of sexR. John Aitken and Jennifer A. Marshal Graves
“The Y chromosome is particularly vulnerable … because it is not a matching partner for the X chromosome, so it cannot retrieve lost genetic information by recombination….
The original Y chromosome contained around 1,500 genes, but during the ensuing 300 million years all but about 50 were inactivated or lost….
At the present rate of decay, the Y chromosome will self-destruct in around 10 million years.”
Spermatogenic Specialization of Y Revealed by Genomic Analyses
• DNA sequence of chromosome
• Catalog of genes
• Y deletions spermatogenic failure
The MSY, the Male-Specific Regionof the Human Y Chromosome
The MSY differs from other nuclearchromosomes:
p q
Euchromatin23 Mb ≈ 1% of human genome Heterochromatin
--specific to one sex --no crossing over
MSY Euchromatin: Three Sequence Classes
p q
Y-specific repeated blocks (amplicons) comprise one third of MSY’s euchromatic DNA
X-transposed (99% X-Y identity)X-degenerateAmpliconic
Skaletsky et al., Nature 423: 825 (2003)
9 Testis-Specific MSY Gene Families:60 Members, All Located in Amplicons
TSPY
VCY
PRY
BPY2
DAZ
RBMY
CDY
XKRY
HSFY
Skaletsky et al., Nature 423: 825 (2003)
Structure of an MSY Palindrome
99.9% - 99.99% identity
up to 1.5 million bp
1 or more testis genes
1 or more testis genes
Skaletsky et al., Nature 423: 825 (2003)
8 Palindromes and 1 Inverted RepeatComprise 25% of MSY Euchromatin
YqYp
HSFY
RBMYPRY
VCY
BPY2
DAZ
CDY
8 6 5 4 3 127 IR2
XKRY
Skaletsky et al., Nature 423: 825 (2003)
Two Forms of Productive Recombination in Human Y Chromosome
1. X-Y crossing-over in pseudoautosomal regions
2. Y-Y gene conversion in portions of MSYconsisting of nearly identical sequence pairs,e.g., palindromes
Yp Yq
Male-specific region
Old and New Understandings of the MSY
genetic wasteland
full of junky repeats
no productive recombination all genes disintegrating
(Muller’s Ratchet)
~76 protein-coding genes
spermatogenic specialization27 distinct proteins;
gene-rich palindromes of unprecedented scale + precision
gene conversion method of preserving gene integrity?